Final answer:
Secretion is the process by which substances are moved from the blood into the distal tubule or collecting tubule, which contrasts with reabsorption.
Step-by-step explanation:
The process of secretion is the movement of substances from the blood into the distal tubule or the collecting tubule. Secretion in the distal convoluted tubule (DCT) refers to the transfer of materials from peritubular capillaries into the renal tubular lumen. This is a crucial step in the formation of urine and helps maintain the homeostasis of water and mineral salts in the bloodstream.
Hormones such as aldosterone play a significant role by increasing the amount of Na+/K+ ATPase, which in turn affects the concentration gradients that drive the secretion process. Moreover, secretion contrasts with reabsorption, where substances are transferred from the filtrate back into the bloodstream. An example of secretion is the movement of potassium and hydrogen ions into the urine, while sodium, chloride, and bicarbonate ions are reabsorbed to maintain pH and electrolyte balance.